Chunk #21 — Results — Differential dopamine release dynamics in the core versus shell relative to cocaine-reinforced responding during self-administration
Similar changes in dopamine signaling in the core and shell were maintained across all animals and recording sites, as shown in Figure 2. As previously reported (Phillips et al., 2003b), the pre-response component of dopamine release in the core was variable in its synchronization to the lever press and therefore was diminished in the average trace in Figure 2A. As in prior reports (Phillips et al., 2003b; Stuber et al., 2005b), rats typically move around the chamber to varying degrees during this time period, then approach and press the lever. A larger increase in [DA] began immediately following the operant response and peaked at 2–3 s following response completion (maximum mean [DA] was 30.8 ± 8.9 nM). A one-way analysis of variance (ANOVA) of mean [DA] in the core revealed significant increases in dopamine relative to the lever press response for intravenous cocaine (F19,171 = 3.034, p < 0.001) that occurred from 1 to 4 s following response completion compared to baseline (Dunnett’s multiple comparison test, p < 0.05).
